It is known that the life of a rolling bearing depends on a load applied to the bearing, a lubrication condition, a material that forms a bearing part, and the like. The life of the rolling bearing can be calculated by using a life calculation equation created in consideration of the aforementioned load, lubrication condition, material and the like (refer to, for example, “Dynamic Load Capacity of Rolling Bearing and Roller Bearing: Detailed Explanation of Lundberg-Palmgren Theory” (NPD 1)). This calculation equation is used to estimate how long the rolling bearing can be used when the rolling bearing is used under a certain condition or to estimate under what condition the rolling bearing should be used in order to prevent the rolling bearing from being broken during the requested time.
Generally, the rolling bearing is used under a use condition set based on the life calculation equation. Therefore, as long as the rolling bearing is used under a normal condition, the life of the rolling bearing does not matter. In the market, however, there often arises a situation in which the life of the rolling bearing becomes an issue. One cause for this is considered to be that the actual use condition of the rolling bearing is different from the scheduled condition. In order to deal with such a situation, there has been proposed a method for analyzing an actually used rolling bearing and estimating the remaining life of the rolling bearing (refer to, for example, Noriyuki Tsushima et al., Bearing Engineer 49, 1984, 25-34(NPD 2)). This method is a method using the fact that a result of stress measurement (stress, half-value width, amount of remaining austenite) with X-ray diffraction has a relation with the rolling time (operating time) of the rolling bearing.